How to assign array range to variable including the "end"-specifier?

I need to assign an array range to a variable (e.g A = B(range), where range=2:40), but with the use of the "end"-specifier, something like:

range = 2:end; A = B(range);

I know that "end" needs information about a certain array to get a value.

My question is: Is it possible to specify "range" in such a way that A = B(range) interprets "range" to be 2:end at runtime?

Answer 1

[Guillaume]

Matlab cannot guess that when you write

 range = 2:end;

The end means the end of another array, B in this case. In any case, end is just a shortcut for size(arraybeingindexed, dimensionbeingindexed), or for vectors numel(vectorbeingindexed). So you could simply write:

range = 2:numel(B);
A = B(range);

[Jon Coll Mossige]

Hi!

Thanks for a good, understandable answer. I have now edited the question slightly, as the former one was poorly defined. -J

[Guillaume]

After your edit, I'm afraid the answer is still it's not possible.

Unless you're willing to change the way you index into B and willing to change the way you create the range. In which case, you could create a function that basically replicates what the |colon operator does:

function values = indexer(indexed, varargin)
    %indexed: variable to be indexed
    %varargin: variable number of index vectors corresponding to each dimension of indexed, of the form
    % [b]: single index
    % [a b]: range of indices from a to b
    % [a s b]: range of indices from a to b with step s
    % in all cases, b can be specified as +Inf to indicates maximum range in the corresponding dimension of indexed
    indexes = cell(size(varargin));
    for dimension = 1:numel(varargin)
        index = varargin{dimension};
        if index(end) == Inf
            if numel(varargin) == 1  %linear indexing
                stop = numel(indexed)
            else                      %subscript indexing
                stop = size(indexed, dimension);
            end
        else
            stop = index(end);
        end
        if numel(index) == 3 %[start step stop]
            step = index(2);
        else
            step = 1;
        end
        indexes{dimension} = start:step:stop;
    end
    values = indexed(indexes{:});
end

Which you could use for example as:

B = 1:randi(500)+20;
range = [5 Inf];
C = indexer(B, range);

The way I've written it, it works on any dimension:

B = rand(10, 20, 30);
rangecol = [10 Inf];
C = indexer(B, [1 5], rangecol, [2 2 6]);

Answer 2

[Stephen23]

The simplest solution (why waste your time?):

 beg = 2;
 B = A(beg:end)